Kinase-inactivated ULK proteins inhibit autophagy via their conserved C-terminal domains using an Atg13-independent mechanism.
The yeast Atg1 serine/threonine protein kinase and its mammalian homologs ULK1 and ULK2 play critical roles during the activation of autophagy. Previous studies have demonstrated that the conserved C-terminal domain (CTD) of ULK1 controls the regulatory function and localization of the protein. Here, we explored the role of kinase activity and intramolecular interactions to further understand ULK function. We demonstrate that the dominant-negative activity of kinase-dead mutants requires a 7-residue motif within the CTD. Our data lead to a model in which the functions of ULK1 and ULK2 are controlled by autophosphorylation and conformational changes involving exposure of the CTD. Additional mapping indicates that the CTD contains other distinct regions that direct membrane association and interaction with the putative human homologue of Atg13, which we have here characterized. Atg13 is required for autophagy and Atg9 trafficking during autophagy. However, Atg13 does not bind the 7-residue dominant-negative motif in the CTD of ULK proteins nor is the inhibitory activity of the CTDs rescued by Atg13 ectopic expression, suggesting that in mammalian cells, the CTD may interact with additional autophagy proteins.
Chan
Edmond Y W
EY
Secretory Pathways Laboratory, London Research Institute, Cancer Research UK, 44 Lincoln's Inn Fields, London WC2A 3PX, United Kingdom.
Longatti
Andrea
A
McKnight
Nicole C
NC
Tooze
Sharon A
SA
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001343:Autophagy; D000071189:Autophagy-Related Protein-1 Homolog; D000071183:Autophagy-Related Proteins; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D017124:Conserved Sequence; D004789:Enzyme Activation; D005799:Genes, Dominant; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000378:metabolism*; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid
C534291:ATG13 protein, human; D048868:Adaptor Proteins, Signal Transducing; D000071183:Autophagy-Related Proteins; D047908:Intracellular Signaling Peptides and Proteins; D050505:Mutant Proteins; D021382:Protein Sorting Signals; C401061:Ulk2 protein, mouse; D000071189:Autophagy-Related Protein-1 Homolog; D017346:Protein Serine-Threonine Kinases; C484754:ULK1 protein, human; C112444:Ulk1 protein, mouse